Integration of barrier layer and seed layer

ABSTRACT

The present invention generally relates to filling of a feature by depositing a barrier layer, depositing a seed layer over the barrier layer, and depositing a conductive layer over the seed layer. In one embodiment, the seed layer comprises a copper alloy seed layer deposited over the barrier layer. For example, the copper alloy seed layer may comprise copper and a metal, such as aluminum, magnesium, titanium, zirconium, tin, and combinations thereof. In another embodiment, the seed layer comprises a copper alloy seed layer deposited over the barrier layer and a second seed layer deposited over the copper alloy seed layer. The copper alloy seed layer may comprise copper and a metal, such as aluminum, magnesium, titanium, zirconium, tin, and combinations thereof. The second seed layer may comprise a metal, such as undoped copper. In still another embodiment, the seed layer comprises a first seed layer and a second seed layer. The first seed layer may comprise a metal, such as aluminum, magnesium, titanium, zirconium, tin, and combinations thereof. The second seed layer may comprise a metal, such as undoped copper.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of co-pending U.S. patent applicationSer. No. 09/965,373, filed Sep. 26, 2001, which is herein incorporatedby reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to an apparatus and method ofdepositing a barrier layer and a seed layer over the barrier layer. Moreparticularly, the present invention relates to an apparatus and methodof depositing a barrier layer and depositing a seed layer comprisingcopper and another metal over the barrier layer.

2. Description of the Related Art

Reliably producing sub-micron and smaller features is one of the keytechnologies for the next generation of very large scale integration(VLSI) and ultra large scale integration (ULSI) of semiconductordevices. However, as the fringes of circuit technology are pressed, theshrinking dimensions of interconnects in VLSI and ULSI technology haveplaced additional demands on the processing capabilities. The multilevelinterconnects that lie at the heart of this technology require preciseprocessing of high aspect ratio features, such as vias and otherinterconnects. Reliable formation of these interconnects is veryimportant to VLSI and ULSI success and to the continued effort toincrease circuit density and quality of individual substrates.

As circuit densities increase, the widths of vias, contacts and otherfeatures, as well as the dielectric materials between them, decrease tosub-micron dimensions (e.g., less than 0.20 micrometers or less),whereas the thickness of the dielectric layers remains substantiallyconstant, with the result that the aspect ratios for the features, i.e.,their height divided by width, increase. Many traditional depositionprocesses have difficulty filling sub-micron structures where the aspectratio exceeds 4:1, and particularly where the aspect ratio exceeds 10:1.Therefore, there is a great amount of ongoing effort being directed atthe formation of substantially void-free and seam-free sub-micronfeatures having high aspect ratios.

Currently, copper and its alloys have become the metals of choice forsub-micron interconnect technology because copper has a lowerresistivity than aluminum, (1.7 μΩ-cm compared to 3.1 μΩ-cm foraluminum), and a higher current carrying capacity and significantlyhigher electromigration resistance. These characteristics are importantfor supporting the higher current densities experienced at high levelsof integration and increased device speed. Further, copper has a goodthermal conductivity and is available in a highly pure state.

Copper metallization can be achieved by a variety of techniques. Atypical method generally comprises physical vapor depositing a barrierlayer over a feature, physical vapor depositing a copper seed layer overthe barrier layer, and then electroplating a copper conductive materiallayer over the copper seed layer to fill the feature. Finally, thedeposited layers and the dielectric layers are planarized, such as bychemical mechanical polishing (CMP), to define a conductive interconnectfeature.

However, one problem with the use of copper is that copper diffuses intosilicon, silicon dioxide, and other dielectric materials which maycompromise the integrity of devices. Therefore, conformal barrier layersbecome increasingly important to prevent copper diffusion. Tantalumnitride has been used as a barrier material to prevent the diffusion ofcopper into underlying layers. One problem with prior uses of tantalumnitride and other barrier layers, however, is that these barrier layersare poor wetting agents for the deposition of copper thereon which maycause numerous problems. For example, during deposition of a copper seedlayer over these barrier layers, the copper seed layer may agglomerateand become discontinuous, which may prevent uniform deposition of acopper conductive material layer (i.e., electroplating of a copperlayer) over the copper seed layer. In another example, subsequentprocessing at high temperatures of a substrate structure having a copperlayer deposited over these barrier layers may cause dewetting and theformation of voids in the copper layer. In still another example,thermal stressing of formed devices through use of the devices may causethe generation of voids in the copper layer and device failure. Thus,there is a need for an improved interconnect structure and method ofdepositing the interconnect structure.

SUMMARY OF THE INVENTION

The present invention generally relates to filling of a feature bydepositing a barrier layer, depositing a seed layer over the barrierlayer, and depositing a conductive layer over the seed layer. In oneembodiment; the seed layer comprises a copper alloy seed layer depositedover the barrier layer. For example, the copper alloy seed layer maycomprise copper and a metal, such as aluminum, magnesium, titanium,zirconium, tin, and combinations thereof. In another embodiment, theseed layer comprises a copper alloy seed layer deposited over thebarrier layer and a second seed layer deposited over the copper alloyseed layer. The copper alloy seed layer may comprise copper and a metal,such as aluminum, magnesium, titanium, zirconium, tin, and combinationsthereof of. The second seed layer may comprise a metal, such as undopedcopper. In still another embodiment, the seed layer comprises a firstseed layer and a second seed layer. The first seed layer may comprise ametal, such as aluminum, magnesium, titanium, zirconium, tin, andcombinations thereof. The second seed layer may comprise a metal, suchas undoped copper.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features, advantages andobjects of the present invention are attained and can be understood indetail, a more particular description of the invention, brieflysummarized above, may be had by reference to the embodiments thereofwhich are illustrated in the appended drawings.

It is to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1 is a schematic cross-sectional view of one embodiment of aprocessing system that may be used to form one or more barrier layers byatomic layer deposition.

FIG. 2A is a schematic cross-sectional view of one embodiment of asubstrate having a dielectric layer deposited thereon.

FIG. 2B is a schematic cross-sectional view of one embodiment of abarrier layer formed over the substrate structure of FIG. 2A.

FIGS. 3A-C illustrate one embodiment of alternating chemisorption ofmonolayers of a tantalum containing compound and a nitrogen containingcompound on a portion of substrate at a stage of barrier layerformation.

FIG. 4 is a schematic cross-sectional view of one embodiment of aprocess system capable of physical vapor deposition which may be used todeposit a copper alloy seed layer.

FIGS. 5A-C are schematic cross-sectional views of embodiments ofdepositing a seed layer over a barrier layer of FIG. 2B.

FIG. 6 is a schematic top-view diagram of one example of a multi-chamberprocessing system which may be adapted to perform processes as disclosedherein.

DETAILED DESCRIPTION

Process Chamber Adapted for Depositing a Barrier Layer

FIG. 1 is a schematic cross-sectional view of one exemplary embodimentof a processing system 10 that may be used to form one or more barrierlayers by atomic layer deposition in accordance with aspects of thepresent invention. Of course, other processing systems may also be used.

The process system 10 generally includes a process chamber 100, a gaspanel 130, a control unit 110, a power supply 106, and a vacuum pump102. The process chamber 100 generally houses a support pedestal 150,which is used to support a substrate such as a semiconductor wafer 190within the process chamber 100.

In the chamber 100, the support pedestal 150 may be heated by anembedded heating element 170. For example, the pedestal 150 may beresistively heated by applying an electric current from an AC powersupply to the heating element 170. The wafer 190 is, in turn, heated bythe pedestal 150, and may be maintained within a desired processtemperature range, for example, between about 20° C and about 1,000° C.depending on the specific process.

A temperature sensor 172, such as a thermocouple, may be embedded in thewafer support pedestal 150 to monitor the pedestal temperature. Forexample, the measured temperature may be used in a feedback loop tocontrol electric current applied to the heating element 170 from thepower supply 106, such that the wafer temperature can be maintained orcontrolled at a desired temperature or within a desired temperaturerange suitable for a certain process application. The pedestal 150 mayalso be heated using radiant heat (not shown) or other heating methods.

The vacuum pump 102 may be used to evacuate process gases from theprocess chamber 100 and may be used to help maintain a desired pressureor desired pressure within a pressure range inside the chamber 100. Anorifice 120 through a wall of the chamber 100 is used to introduceprocess gases into the process chamber 100. The size of the orifice 120conventionally depends on the size of the process chamber 100.

The orifice 120 is coupled to the gas panel 130 in part by a valve 125.The gas panel 130 may be configured to receive and then provide aresultant process gas from two or more gas sources 135, 136 to theprocess chamber 100 through the orifice 120 and the valve 125. The gassources 135, 136 may store precursors in a liquid phase at roomtemperature, which are later heated when in the gas panel 130 to convertthem to a vapor-gas phase for introduction into the chamber 100. The gassources 135, 136 may also be adapted to provide precursors through theuse of a carrier gas. The gas panel 130 may be further configured toreceive and then provide a purge gas from a purge gas source 138 to theprocess chamber 100 through the orifice 120 and the valve 125. Ashowerhead 160 may be coupled to the orifice 120 to deliver a processgas, purge gas, or other gas toward the wafer 190 on the supportpedestal 150.

The showerhead 160 and the support pedestal 150 may serve as spacedapart electrodes for providing an electric field for igniting a plasma.A RF power source 162 may be coupled to the showerhead 160, a RF powersource 163 may be coupled to the support pedestal 150, or RF powersources 162, 163 may be coupled to the showerhead 160 and the supportpedestal 150, respectively. A matching network 164 may be coupled to theRF power sources 162, 163, which may be coupled to the control unit 110to control the power supplied to the RF power sources 162, 163.

The control unit 110, such as a programmed personal computer, workstation computer, and the like, may also be configured to control flowof various process gases through the gas panel 130 as well as the valve125 during different stages of a wafer process sequence. Illustratively,the control unit 110 comprises a central processing unit (CPU) 112,support circuitry 114, and memory 116 containing associated controlsoftware 113. In addition to control of process gases through the gaspanel 130, the control unit 110 may be configured to be responsible forautomated control of other activities used in wafer processing-such aswafer transport, temperature control, chamber evacuation, among otheractivities, some of which are described elsewhere herein.

The control unit 110 may be one of any form of general purpose computerprocessor that can be used in an industrial setting for controllingvarious chambers and sub-processors. The CPU 112 may use any suitablememory 116, such as random access memory, read only memory, floppy diskdrive, hard disk, or any other form of digital storage, local or remote.Various support circuits may be coupled to the CPU 112 for supportingthe system 10. Software routines 113 as required may be stored in thememory 116 or executed by a second computer processor that is remotelylocated (not shown). Bi-directional communications between the controlunit 110 and various other components of the wafer processing system 10are handled through numerous signal cables collectively referred to assignal buses 118, some of which are illustrated in FIG. 1.

Barrier Layer Formation

The exemplary chamber as described in FIG. 1 may be used to implementthe following process. Of course, other process chambers may be used.FIGS. 2A-2B illustrate one exemplary embodiment of barrier layerformation for fabrication of an interconnect structure in accordancewith one or more aspects of the present invention.

FIG. 2A is a schematic cross-sectional view of one embodiment of asubstrate 200 having a dielectric layer 202 deposited thereon. Dependingon the processing stage, the substrate 200 may be a siliconsemiconductor wafer, or other material layer, which has been formed onthe wafer. The dielectric layer 202 may be an oxide, a silicon oxide,carbon-silicon-oxide, a fluoro-silicon, a porous dielectric, or othersuitable dielectric formed and patterned to provide a contact hole orvia 202H extending to an exposed surface portion 202T of the substrate200. For purposes of clarity, the substrate 200 refers to any workpieceupon which film processing is performed, and a substrate structure 250is used to denote the substrate 200 as well as other material layersformed on the substrate 200, such as the dielectric layer 202. It isalso understood by those with skill in the art that the presentinvention may be used in a dual damascene process flow.

FIG. 2B is a schematic cross-sectional view of one embodiment of abarrier layer 204 formed over the substrate structure 250 of FIG. 2A byatomic layer deposition (ALD). Preferably, the barrier layer comprises atantalum nitride layer. Examples of other barrier layer materials whichmay be used include titanium (Ti), titanium nitride (TiN), titaniumsilicon nitride (TiSiN), tantalum (Ta), tantalum silicon nitride(TaSiN), tungsten (W), tungsten nitride (WN), tungsten silicon nitride(WSiN), and combinations thereof.

For clarity reasons, deposition of the barrier layer will be describedin more detail in reference to one embodiment of the barrier layercomprising a tantalum nitride barrier layer. In one aspect, atomic layerdeposition of a tantalum nitride barrier layer comprises sequentiallyproviding a tantalum containing compound and a nitrogen containingcompound to a process chamber, such as the process chamber of FIG. 1.Sequentially providing a tantalum containing compound and a nitrogencontaining compound may result in the alternating chemisorption ofmonolayers of a tantalum containing compound and of monolayers of anitrogen containing compound on the substrate structure 250.

FIGS. 3A-C illustrate one embodiment of the alternating chemisorption ofmonolayers of a tantalum containing compound and a nitrogen containingcompound on an exemplary portion of substrate 300 in a stage ofintegrated circuit fabrication, and more particularly at a stage ofbarrier layer formation. In FIG. 3A, a monolayer of a tantalumcontaining compound is chemisorbed on the substrate 300 by introducing apulse of the tantalum containing compound 305 into a process chamber,such as a process chamber shown in FIG. 1. It is believed that thechemisorption processes used to absorb the monolayer of the tantalumcontaining compound 305 are self-limiting in that only one monolayer maybe chemisorbed onto the surface of the substrate 300 during a givenpulse because the surface of the substrate has a finite number of sitesfor chemisorbing the tantalum containing compound. Once the finitenumber of sites is occupied by the tantalum containing compound 305,further chemisorption of any tantalum containing compound will beblocked.

The tantalum containing compound 305 typically comprises tantalum atoms310 with one or more reactive species 315. In one embodiment, thetantalum containing compound may be a tantalum based organometallicprecursor or a derivative thereof. Preferably, the organometallicprecursor is penta(dimethylamino)-tantalum (PDMAT; Ta(NMe₂)₅). PDMAT maybe used to advantage for a number of reasons. PDMAT is relativelystable. PDMAT has an adequate vapor pressure which makes it easy todeliver. In particular, PDMAT may be produced with a low halide content.The halide content of PDMAT may be produced with a halide content ofless than 100 ppm, and may even be produced with a halide content ofless than 30 ppm or even less than 5 ppm. Not wishing to be bound bytheory, it is believed that an organometallic precursor with a lowhalide content is beneficial because halides (such as chlorine)incorporated in the barrier layer may attack the copper layer depositedthereover.

The tantalum containing compounds may be other organometallic precursorsor derivatives thereof such as, but not limited topenta(ethylmethylamino)-tantalum (PEMAT; Ta(N(Et)Me)₅),penta(diethylamino)-tantalum (PDEAT; Ta(NEt₂)₅), and any and all ofderivatives of PEMAT, PDEAT, or PDMAT. Other tantalum containingcompounds include without limitation TBTDET (Ta(NEt₂)₃NC₄H₉ orC₁₆H₃₉N₄Ta) and tantalum halides, for example TaX₅ where X is fluorine(F), bromine (Br) or chlorine (Cl), and derivatives thereof.

The tantalum containing compound may be provided as a gas or may beprovided with the aid of a carrier gas. Examples of carrier gases whichmay be used include, but are not limited to, helium (He), argon (Ar),nitrogen (N₂), and hydrogen (H₂).

After the monolayer of the tantalum containing compound is chemisorbedonto the substrate 300, excess tantalum containing compound is removedfrom the process chamber by introducing a pulse of a purge gas thereto.Examples of purge gases which may be used include, but are not limitedto, helium (He), argon (Ar), nitrogen (N₂), hydrogen (H₂), and othergases.

Referring to FIG. 3B, after the process chamber has been purged, a pulseof a nitrogen containing compound 325 is introduced into the processchamber. The nitrogen containing compound 325 may be provided alone ormay be provided with the aid of a carrier gas. The nitrogen containingcompound 325 may comprise nitrogen atoms 330 with one or more reactivespecies 335. The nitrogen containing compound preferably comprisesammonia gas (NH₃). Other nitrogen containing compounds may be used whichinclude, but are not limited to, N_(x)H_(y) with x and y being integers(e.g., hydrazine (N₂H₄)), dimethyl hydrazine ((CH₃)₂N₂H₂),t-butylhydrazine (C₄H₉N₂H₃), phenylhydrazine (C₆H₅N₂H₃), other hydrazinederivatives, a nitrogen plasma source (e.g., N₂, N₂/H₂, NH₃, or a N₂H₄plasma), 2,2′-azotertbutane ((CH₃)₆C₂N₂), ethylazide (C₂H₅N₃), and othersuitable gases. A carrier gas may be used to deliver the nitrogencontaining compound if necessary.

A monolayer of the nitrogen containing compound 325 may be chemisorbedon the monolayer of the tantalum containing compound 305. Thecomposition and structure of precursors on a surface during atomic-layerdeposition (ALD) is not precisely known. Not wishing to be bound bytheory, it is believed that the chemisorbed monolayer of the nitrogencontaining compound 325 reacts with the monolayer of the tantalumcontaining compound 305 to form a tantalum nitride layer 309. Thereactive species 315, 335 form by-products 340 that are transported fromthe substrate surface by the vacuum system. It is believed that thereaction of the nitrogen containing compound 325 with the tantalumcontaining compound 305 is self-limited since only one monolayer of thetantalum containing compound 305 was chemisorbed onto the substratesurface. In another theory, the precursors may be in an intermediatestate when on a surface of the substrate. In addition, the depositedtantalum nitride layer may also contain more than simply elements oftantalum (Ta) or nitrogen (N); rather, the tantalum nitride layer mayalso contain more complex molecules having carbon (C), hydrogen (H),and/or oxygen (0).

After the monolayer of the nitrogen containing compound 325 ischemisorbed on the monolayer of the tantalum containing compound, anyexcess nitrogen containing compound is removed from the process chamberby introducing another pulse of the purge gas therein. Thereafter, asshown in FIG. 3C, the tantalum nitride layer deposition sequence ofalternating chemisorption of monolayers of the tantalum containingcompound and of the nitrogen containing compound may be repeated, ifnecessary, until a desired tantalum nitride thickness is achieved.

In FIGS. 3A-3C, the tantalum nitride layer formation is depicted asstarting with the chemisorption of a monolayer of a tantalum containingcompound on the substrate followed by a monolayer of a nitrogencontaining compound. Alternatively, the tantalum nitride layer formationmay start with the chemisorption of a monolayer of a nitrogen containingcompound on the substrate followed by a monolayer of the tantalumcontaining compound. Furthermore, in an alternative embodiment, a pumpevacuation alone between pulses of reactant gases may be used to preventmixing of the reactant gases.

The time duration for each pulse of the tantalum containing compound,the nitrogen containing compound, and the purge gas is variable anddepends on the volume capacity of a deposition chamber employed as wellas a vacuum system coupled thereto. For example, (1) a lower chamberpressure of a gas will require a longer pulse time; (2) a lower gas flowrate will require a longer time for chamber pressure to rise andstabilize requiring a longer pulse time; and (3) a large-volume chamberwill take longer to fill, longer for chamber pressure to stabilize thusrequiring a longer pulse time. Similarly, time between each pulse isalso variable and depends on volume capacity of the process chamber aswell as the vacuum system coupled thereto. In general, the time durationof a pulse of the tantalum containing compound or the nitrogencontaining compound should be long enough for chemisorption of amonolayer of the compound. In general, the pulse time of the purge gasshould be long enough to remove the reaction by-products and/or anyresidual materials remaining in the process chamber.

Generally, a pulse time of about 1.0 second or less for a tantalumcontaining compound and a pulse time of about 1.0 second or less for anitrogen containing compound are typically sufficient to chemisorbalternating monolayers on a substrate. A pulse time of about 1.0 secondor less for a purge gas is typically sufficient to remove reactionby-products as well as any residual materials remaining in the processchamber. Of course, a longer pulse time may be used to ensurechemisorption of the tantalum containing compound and the nitrogencontaining compound and to ensure removal of the reaction by-products.

During atomic layer deposition, the substrate may be maintainedapproximately below a thermal decomposition temperature of a selectedtantalum containing compound. An exemplary heater temperature range tobe used with tantalum containing compounds identified herein isapproximately between about 20° C. and about 500° C. at a chamberpressure less than about 100 Torr, preferably less than about 50 Torr.When the tantalum containing gas is PDMAT, the heater temperature ispreferably between about 100° C. and about 300° C., more preferablybetween about 175° C. and about 250° C. In other embodiments, it shouldbe understood that other temperatures may be used. For example, atemperature above a thermal decomposition temperature may be used.However, the temperature should be selected so that more than 50 percentof the deposition activity is by chemisorption processes. In anotherexample, a temperature above a thermal decomposition temperature may beused in which the amount of decomposition during each precursordeposition is limited so that the growth mode will be similar to anatomic layer deposition growth mode.

One exemplary process of depositing a tantalum nitride layer by atomiclayer deposition in a process chamber, such as the process chamber ofFIG. 1, comprises sequentially providing penta(dimethylamino)-tantalum(PDMAT) at a flow rate between about 100 sccm and about 1,000 sccm, andpreferably between about 200 sccm and about 500 sccm, for a time periodof about 1.0 second or less, providing ammonia at a flow rate betweenabout 100 sccm and about 1,000 sccm, preferably between about 200 sccmand about 500 sccm, for a time period of about 1.0 second or less, and apurge gas at a flow rate between about 100 sccm and about 1,000 sccm,preferably between about 200 sccm and about 500 sccm for a time periodof about 1.0 second or less. The heater temperature preferably ismaintained between about 100° C. and about 300° C. at a chamber pressurebetween about 1.0 Torr and about 5.0 Torr. This process provides atantalum nitride layer in a thickness between about 0.5 Å and about 1.0Å per cycle. The alternating sequence may be repeated until a desiredthickness is achieved.

In one embodiment, the barrier layer, such as a tantalum nitride barrierlayer, is deposited to a sidewall coverage of about 50 Å or less. Inanother embodiment, the barrier layer is deposited to a sidewallcoverage of about 20 Å or less. In still another embodiment, the barrierlayer is deposited to a sidewall coverage of about 10 Å or less. Abarrier layer with a thickness of about 10 Å or less is believed to be asufficient barrier layer to prevent copper diffusion. In one aspect, athin barrier layer may be used to advantage in filling sub-micron andsmaller features having high aspect ratios. Of course, a barrier layerhaving a sidewall coverage of greater than 50 Å may be used.

The barrier layer may be further plasma annealed. In one embodiment, thebarrier lay may be plasma annealed with an argon plasma or anargon/hydrogen plasma. The RF power supplied to an RF electrode may bebetween about 100 W and about 2,000 W, preferably between about 500 Wand about 1,000 W for a 200 mm diameter substrate and preferably betweenabout 1,000 W and about 2,000 W for a 300 mm diameter substrate. Thepressure of the chamber may be less than 100 Torr, preferably betweenabout 0.1 Torr and about 5 Torr, and more preferably between about 1Torr and 3 Torr. The heater temperature may be between about 20° C. andabout 500° C. The plasma anneal may be performed after a cycle, aplurality of cycles, or after formation of the barrier layer.

Embodiments of atomic layer deposition of the barrier layer have beendescribed above as chemisorption of a monolayer of reactants on asubstrate. The present invention also includes embodiments in which thereactants are deposited to more or less than a monolayer. The presentinvention also includes embodiments in which the reactants are notdeposited in a self-limiting manner. The present invention also includesembodiments in which the barrier layer 204 is deposited in mainly achemical vapor deposition process in which the reactants are deliveredsequentially or simultaneously. The present invention also includesembodiments in which the barrier layer 204 is deposited in a physicalvapor deposition process in which the target comprises the material tobe deposited (i.e., a tantalum target in a nitrogen atmosphere for thedeposition of tantalum nitride).

Process Chamber Adapted for Depositing a Seed Layer

In one embodiment, the seed layer may be deposited by any suitabletechnique such as physical vapor deposition, chemical vapor deposition,electroless deposition, or a combination of techniques. Suitablephysical vapor deposition techniques for the deposition of the seedlayer include techniques such as high density plasma physical vapordeposition (HDP PVD) or collimated or long throw sputtering. One type ofHDP PVD is self-ionized plasma physical vapor deposition. An example ofa chamber capable of self-ionized plasma physical vapor deposition of aseed layer is a SIP™ chamber, available from Applied Materials, Inc., ofSanta Clara, Calif. Exemplary embodiments of chambers capable ofself-ionized physical vapor deposition are described in U.S. Pat. No.6,183,614, entitled “Rotating Sputter Magnetron Assembly,” which isherein incorporated by reference to the extent not inconsistent with thepresent invention.

FIG. 4 is a schematic cross-sectional view of one embodiment of aprocess system 410 capable of physical vapor deposition which may beused to deposit a seed layer. Of course, other processing systems andother types of physical vapor deposition may also be used.

The process system 410 includes a chamber 412 sealed to a PVD target 414composed of the material to be sputter deposited on a wafer 416 held ona heater pedestal 418. A shield 420 held within the chamber protects thewalls of the chamber 412 from the sputtered material and provides theanode grounding plane. A selectable DC power supply 422 negativelybiases the target 414 with respect to the shield 420.

A gas source 424 supplies a sputtering working gas, typically thechemically inactive gas argon, to the chamber 412 through a mass flowcontroller 426. A vacuum system 428 maintains the chamber at a lowpressure. A computer-based controller 430 controls the reactor includingthe DC power supply 422 and the mass flow controllers 426.

When the argon is admitted into the chamber, the DC voltage between thetarget 414 and the shield 420 ignites the argon into a plasma, and thepositively charged argon ions are attracted to the negatively chargedtarget 414. The ions strike the target 414 at a substantial energy andcause target atoms or atomic clusters to be sputtered from the target414. Some of the target particles strike the wafer 416 and are therebydeposited on it, thereby forming a film of the target material.

To provide efficient sputtering, a magnetron 432 is positioned in backof the target 414. It has opposed magnets 434, 436 creating a magneticfield within the chamber in the neighborhood of the magnets 434, 436.The magnetic field traps electrons and, for charge neutrality, the iondensity also increases to form a high-density plasma region 438 withinthe chamber adjacent to the magnetron 432. The magnetron 432 usuallyrotates about a rotational axis 458 at the center of the target 414 toachieve full coverage in sputtering of the target 414.

The pedestal 418 develops a DC self-bias, which attracts ionizedsputtered particles from the plasma across the plasma sheath adjacent tothe wafer 416. The effect can be accentuated with additional DC or RFbiasing of the pedestal electrode 418 to additionally accelerate theionized particles extracted across the plasma sheath towards the wafer416, thereby controlling the directionality of sputter deposition.

Seed Layer Formation

The exemplary chamber as described in FIG. 4 may be used to implementthe following process. Of course, other process chambers may be used.FIGS. 5A-5C are schematic cross-sectional view of exemplary embodimentsof depositing a seed layer over a barrier layer.

One embodiment, as shown in FIG. 5A, comprises depositing a copper alloyseed layer 502 over a barrier layer 204 of FIG. 2B and depositing acopper conductive material layer 506 over the copper alloy seed layer502 to fill the feature. The term “copper conductive material layer” asused in the specification is defined as a layer comprising copper or acopper alloy. The copper alloy seed layer 502 comprises a copper metalalloy that aids in subsequent deposition of materials thereover. Thecopper alloy seed layer 502 may comprise copper and a second metal, suchas aluminum, magnesium, titanium, zirconium, tin, other metals, andcombinations thereof. The second metal preferably comprises aluminum,magnesium, titanium, and combinations thereof and more preferablycomprises aluminum. In certain embodiments, the copper alloy seed layercomprises a second metal in a concentration having the lower limits ofabout 0.001 atomic percent, about 0.01 atomic percent, or about 0.1atomic percent and having the upper limits of about 5.0 atomic percent,about 2.0 atomic percent, or about 1.0 atomic percent. The concentrationof the second metal in a range from any lower limit to any upper limitis within the scope of the present invention. The concentration of thesecond metal in the copper alloy seed layer 502 is preferably less thanabout 5.0 atomic percent to lower the resistance of the copper alloyseed layer 502. The term “layer” as used in the specification is definedas one or more layers. For example, for a copper alloy seed layer 502comprising copper and a second metal in a concentration in a rangebetween about 0.001 atomic percent and about 5.0 atomic percent, thecopper alloy seed layer 502 may comprise a plurality of layers in whichthe total composition of the layers comprises copper and the secondmetal in a concentration between about 0.001 atomic percent and about5.0 atomic percent. For illustration, examples of a copper alloy seedlayer 502 comprising a plurality of layers in which the totalcomposition of the layers comprises copper and the second metal in aconcentration between about 0.001 atomic percent and about 5.0 atomicpercent may comprises a first seed layer comprising the second metal anda second seed layer comprising copper, may comprise a first seed layercomprising a copper/second metal alloy and a second seed layercomprising a copper/second metal alloy, or may comprise a first seedlayer comprising a copper/second metal alloy and a second seed layercomprising copper.

The copper alloy seed layer 502 is deposited to a thickness of at leastabout a 5 Å coverage of the sidewalls of the feature or to a thicknessof at least a continuous coverage of the sidewalls of the feature. Inone embodiment, the copper alloy seed layer 502 is deposited to athickness at the field areas between about 10 Å and about 2,000 Å,preferably between about 500 Å and about 1,000 Å for a copper alloy seedlayer 502 deposited by physical vapor deposition.

Another embodiment, as shown in FIG. 5B, comprises depositing a copperalloy seed layer 512 over a barrier layer 204 of FIG. 2B, depositing asecond seed layer 514 over the copper alloy seed layer 512, anddepositing a copper conductive material layer 516 over the second seedlayer 514 to fill the feature. The copper alloy seed layer 512 comprisesa copper metal alloy that aids in subsequent deposition of materialsthereover. The copper alloy seed layer 512 may comprise copper and asecond metal, such as aluminum, magnesium, titanium, zirconium, tin,other metals, and combinations thereof. The second metal preferablycomprises aluminum, magnesium, titanium, and combinations thereof andmore preferably comprises aluminum. In certain embodiments, the copperalloy seed layer comprises a second metal in a concentration having thelower limits of about 0.001 atomic percent, about 0.01 atomic percent,or about 0.1 atomic percent and having the upper limits of about 5.0atomic percent, about 2.0 atomic percent, or about 1.0 atomic percent.The concentration of the second metal in a range from any lower limit toany upper limit is within the scope of the present invention. In oneembodiment, the second seed layer 514 comprises undoped copper (i.e.,pure copper). In one aspect, a second seed layer 514 comprising undopedcopper is used because of its lower electrical resistivity than a copperalloy seed layer 512 of the same thickness and because of its higherresistance to surface oxidation.

The copper alloy seed layer 512 may be deposited to a thickness of lessthan a monolayer (i.e., a sub-monolayer thickness or a discontinuouslayer) over the sidewalls of the feature. In one embodiment, thecombined thickness of the copper alloy seed layer 512 and the secondseed layer 514 at the field areas is between about 10 Å and about 2,000Å, preferably between about 500 Å and about 1,000 Å for a copper alloyseed layer 512 and second seed layer 514 deposited by physical vapordeposition.

Another embodiment, as shown in FIG. 5C, comprises depositing a firstseed layer 523 over a barrier layer 204 of FIG. 2B, depositing a secondseed layer 524 over the first seed layer 523, and depositing a copperconductive material layer 526 over the second seed layer 524 to fill thefeature. The first seed layer 523 comprises a metal selected from thegroup consisting of aluminum, magnesium, titanium, zirconium, tin, andcombinations thereof. Preferably, the first seed layer 523 comprisesaluminum. In one embodiment, the second seed layer 514 comprises undopedcopper (i.e., pure copper).

The first seed layer 523 may be deposited to a thickness of less than amonolayer (i.e., a sub-monolayer thickness or a discontinuous layer)over the sidewalls of the feature. In one embodiment, the first seedlayer is deposited to a thickness of less than about 50 Å sidewallcoverage, preferably less than about 40 Å sidewall coverage, in order tolower the total resistance of the combined seed layer. The combinedthickness of the first seed layer 523 and the second seed layer 524 atthe field areas is between about 10 Å and about 2,000 Å, preferablybetween about 500 Å and about 1,000 Å for a first seed layer 523 andsecond seed layer 524 deposited by physical vapor deposition.

The copper alloy seed layer 502, 512, the first seed layer 523, or thesecond seed layer 514, 524 may be deposited by such techniques includingphysical vapor deposition, chemical vapor deposition, atomic layerdeposition, electroless deposition, or a combination of techniques. Ingeneral, if a seed layer is deposited utilizing physical vapordeposition techniques, a chamber, such as the chamber 412 as describedin FIG. 4, includes a target, such as target 414, having a compositionsimilar to the metal or metal alloy intended to be deposited. Forexample, to deposit a copper alloy seed layer 502, 512 the target maycomprise copper and a second metal, such as aluminum, magnesium,titanium, zirconium, tin, other metals, and combinations thereof. Thesecond metal preferably comprises aluminum. In certain embodiments, thetarget comprises a second metal in a concentration having the lowerlimits of about 0.001 atomic percent, about 0.01 atomic percent, orabout 0.1 atomic percent and having the upper limits of about 5.0 atomicpercent, about 2.0 atomic percent, or about 1.0 atomic percent. Theconcentration of the second metal in a range from any lower limit to anyupper limit is within the scope of the present invention. In anotherexample, to deposit a first seed layer 523, the target comprises a metalselected from the group consisting of aluminum, magnesium, titanium,zirconium, tin, and combinations thereof. If a seed layer is depositedby chemical vapor deposition or atomic layer deposition, a chamber, suchas the chamber as described in FIG. 1, is adapted to deliver suitablemetal precursors of the metal or metal alloy to be deposited.

One exemplary process of depositing a seed layer by physical vapordeposition in a process chamber, such as the process chamber of FIG. 4,comprises utilizing a target of the material to be deposited. Theprocess chamber may be maintained at a pressure of between about 0.1mTorr and about 10 mTorr. The target may be DC-biased at a power betweenabout 5 kW and about 100 kW. The pedestal may be RF-biased at a powerbetween about 0 and about 1,000 W. The pedestal may be unheated (i.e.,room temperature).

The copper conductive material layer 506, 516, 526 may be deposited byelectroplating, physical vapor deposition, chemical vapor deposition,electroless deposition or a combination of techniques. Preferably, thecopper conductive material layer 506, 516, 526 is deposited byelectroplating because of the bottom-up growth which may be obtained inelectroplating processes. An exemplary electroplating method isdescribed in U.S. Pat. No. 6,113,771, entitled “Electro DepositionChemistry,” issued Sep. 5, 2000, and is incorporated herein by referenceto the extent not inconsistent with this invention.

It has been observed that a copper alloy seed layer, such as acopper-aluminum seed layer, has improved adhesion over a barrier layerwhen compared to an undoped copper seed layer over the barrier layer.Because the copper alloy seed layer has good adhesion over a barrierlayer, the copper alloy seed layer acts as a good wetting agent tomaterials deposited thereon. Not wishing to be bound by theory, it isbelieved that the concentration of the copper and other metals of thecopper seed layer provides a seed layer with good wetting properties andgood electrical characteristics. It is further believed that a copperalloy seed layer having a total thickness of less than a monolayer maybe used as long as a second seed layer, such as an undoped seed layer,is deposited thereover to provide at least a combined continuous seedlayer since the copper alloy seed layer provides an improved interfacefor adhesion of materials thereon.

Similarly, it has been observed that a metal seed layer, such as analuminum seed layer, has improved adhesion over a barrier layer whencompared to an undoped copper seed layer over the barrier layer. Becausethe metal seed layer has good adhesion over a barrier layer, the metalseed layer acts as a good wetting agent to materials deposited thereon.Not wishing to bound by theory, it is believed that a metal seed layer,such as an aluminum seed layer, having a total thickness of less than amonolayer may be used since the metal layer provides an improvedinterface for adhesion of materials thereon, such as an undoped copperseed layer deposited over the metal layer.

The seed layers as disclosed herein have improved adhesion over barrierlayers and have good wetting properties for materials depositedthereover, such as a copper conductive material layer depositedthereover. Therefore, the seed layers increase device reliability byreducing the likelihood of agglomeration, dewetting, or the formation ofvoids in the copper conductive material layer during deposition of thecopper conductive material layer, during subsequent processing at hightemperatures, and during thermal stressing of the devices during use ofthe devices.

In one aspect, the seed layers may be used with any barrier layer andmay be used with barrier layers deposited by any deposition technique.The seed layers also may be deposited by any deposition technique.Furthermore, a conductive material layer, such as a copper conductivematerial layer, may be deposited over the seed layers by any depositiontechnique.

The present process may be used to advantage in filling apertures havingless than about 0.2 micron opening width and having an aspect ratio ofgreater than about 4:1, about 6:1; or about 10:1.

The processes as disclosed herein may be carried out in separatechambers or may be carried out in a multi-chamber processing systemhaving a plurality of chambers. FIG. 6 is a schematic top-view diagramof one example of a multi-chamber processing system 600 which may beadapted to perform processes as disclosed herein. The apparatus is anENDURA™ system and is commercially available from Applied Materials,Inc., of Santa Clara, Calif. A similar multi-chamber processing systemis disclosed in U.S. Pat. No. 5,186,718, entitled “Stage Vacuum WaferProcessing System and Method,” (Tepman, et al.), issued on Feb. 16,1993, where is hereby incorporated by reference to the extent notinconsistent with the present disclosure. The particular embodiment ofthe system 600 is provided to illustrate the invention and should not beused to limit the scope of the invention.

The system 600 generally includes load lock chambers 602, 604 for thetransfer of substrates into and out from the system 600. Typically,since the system 600 is under vacuum, the load lock chambers 602, 604may “pump down” the substrates introduced into the system 600. A firstrobot 610 may transfer the substrates between the load lock chambers602, 604, processing chambers 612, 614, transfer chambers 622, 624, andother chambers 616, 618. A second robot 630 may transfer the substratesbetween processing chambers 632, 634, 636, 638 and the transfer chambers622, 624. Processing chambers 612, 614, 632, 634, 636, 638 may beremoved from the system 600 if not necessary for the particular processto be performed by the system 600.

In one embodiment, the system 600 is configured so that processingchamber 634 is adapted to deposit a copper alloy seed layer 502. Forexample, the processing chamber 634 for depositing a copper alloy seedlayer 502 may be a physical vapor deposition chamber, a chemical vapordeposition chamber, or an atomic layer deposition chamber. The system600 may be further configured so that processing chamber 632 is adaptedto deposit a barrier layer 204 in which the copper alloy seed layer 502is deposited over the barrier layer. For example, the processing chamber632 for depositing the barrier layer 204 may be an atomic layerdeposition chamber, a chemical vapor deposition chamber, or a physicalvapor deposition chamber. In one specific embodiment, the processingchamber 632 may be an atomic layer deposition chamber, such as thechamber shown in FIG. 1, and the processing chamber 634 may be aphysical vapor deposition chamber, such as the chamber shown in FIG. 4.

In another embodiment, the system 600 is configured so that processingchamber 634 is adapted to deposit a copper alloy seed layer 512 and sothat processing chamber 636 is adapted to deposit a second seed layer514 over the copper alloy seed layer 512. For example, the processingchamber 634 for depositing a copper alloy seed layer 512 and/or theprocessing chamber 636 for depositing a second seed layer may be aphysical vapor deposition chamber, a chemical vapor deposition chamber,or an atomic layer deposition chamber. The system 600 may be furtherconfigured so that processing chamber 632 is adapted to deposit abarrier layer 204 in which the copper alloy seed layer 512 is depositedover the barrier layer. For example, the processing chamber 632 fordepositing the barrier layer 204 may be an atomic layer depositionchamber, a chemical vapor deposition chamber, or a physical vapordeposition chamber. In one specific embodiment, processing chamber 632may be an atomic layer deposition chamber, such as the chamber shown inFIG. 1, and processing chambers 634, 636 may be physical vapordeposition chambers, such as the chamber shown in FIG. 4.

In another embodiment, the system 600 is configured so that processingchamber 634 is adapted to deposit a metal seed layer 523 and so thatprocessing chamber 636 is adapted to deposit a second seed layer 524over the metal seed layer 523. For example, the processing chamber 634for depositing a metal seed layer 523 and/or the processing chamber 636for depositing a second seed layer 524 may be a physical vapordeposition chamber, a chemical vapor deposition chamber, or an atomiclayer deposition chamber. The system may be further configured so thatprocessing chamber 632 is adapted to deposit a barrier layer 204 inwhich the metal seed layer 523 is deposited over the barrier layer. Forexample, the processing chamber 632 for depositing the barrier layer 204may be an atomic layer deposition chamber, a chemical vapor depositionchamber, or a physical vapor deposition chamber. In one specificembodiment, processing chamber 632 may be an atomic layer depositionchamber, such as the chamber shown in FIG. 1, and processing chambers634, 636 may be physical vapor deposition chambers, such as the chambershown in FIG. 4.

In one aspect, deposition of a barrier layer 204 and a seed layer (suchas a copper alloy seed layer 502, a copper alloy seed layer 512 and asecond seed layer 514, or a metal seed layer 523 and a second seed layer524) may be performed in a multi-chamber processing system under vacuumto prevent air and other impurities from being incorporated into thelayers and to maintain the seed structure over the barrier layer 204.

Other embodiments of the system 600 are within the scope of the presentinvention. For example, the position of a particular processing chamberon the system may be altered. In another example, a single processingchamber may be adapted to deposit two different layers.

EXAMPLES Example 1

A TaN layer was deposited over a substrate by atomic layer deposition toa thickness of about 20 Å. A seed layer was deposited over the TaN layerby physical vapor deposition to a thickness of about 100 Å. The seedlayer comprised either 1) undoped copper deposited utilizing a targetcomprising undoped copper, 2) a copper alloy comprising aluminum in aconcentration of about 2.0 atomic percent deposited utilizing acopper-aluminum target comprising aluminum in a concentration of about2.0 atomic percent, 3) a copper alloy comprising tin in a concentrationof about 2.0 atomic percent deposited utilizing a copper-tin targetcomprising tin in a concentration of about 2.0 atomic percent, or 4) acopper alloy comprising zirconium in a concentration of about 2.0 atomicpercent deposited utilizing a copper-zirconium target comprisingzirconium in a concentration of about 2.0 atomic percent. The resultingsubstrate was annealed at a temperature of about 380° C. for a timeperiod of about 15 minutes in a nitrogen (N₂) and hydrogen (H₂) ambient.

Scanning electron microscope photographs showed agglomeration of theundoped copper layer after the anneal. The copper-zirconium alloy showedless agglomeration than the undoped copper layer. The copper-tin alloyshowed less agglomeration than the copper-zirconium alloy. Thecopper-aluminum alloy showed no significant agglomeration.

Example 2

Copper-aluminum alloy films comprising about 2.0 atomic percent ofaluminum were deposited on different substrates by physical vapordeposition utilizing a copper-aluminum target comprising aluminum in aconcentration of 2.0 atomic percent. The resulting substratesincluded 1) a copper-aluminum layer deposited to a thickness of about 50Å over an ALD TaN layer, 2) a copper-aluminum layer deposited to athickness of about 50 Å over about a 100 Å Ta layer, 3) acopper-aluminum layer deposited to a thickness of about 100 Å over anALD TaN layer, 4) a copper-aluminum layer deposited to a thickness ofabout 100 Å over a silicon nitride (SiN) layer, and 5) a copper-aluminumlayer deposited to a thickness of about 100 Å over a silicon oxidelayer. The resulting substrates were annealed at a temperature of about380° C. for a time period of about 15 minutes in a nitrogen (N₂) andhydrogen (H₂) ambient. Scanning electron microscope photographs showedthat there was no significant agglomeration of the copper-aluminum alloyover the various substrates.

Example 3

Copper-aluminum alloy films comprising about 2.0 atomic percent ofaluminum were deposited by physical vapor deposition utilizing acopper-aluminum target comprising aluminum in a concentration of 2.0atomic percent to either a 50 Å or 100 Å thickness over an ALD TaNlayer. The resulting substrates were annealed at a temperature of about380° C., about 450° C., or about 500° C. for a time period of about 15minutes in a nitrogen (N₂) and hydrogen (H₂) ambient. Scanning electronmicroscope photographs showed that there was no significantagglomeration of the copper-aluminum alloy for substrates annealed attemperatures of about 380° C. or about 450° C. The copper-aluminum alloyshowed some dewetting began to occur for substrates annealed at atemperature of about 500° C.

Example 4

Copper-aluminum alloy films comprising about 2.0 atomic percent ofaluminum were deposited by physical vapor deposition utilizing acopper-aluminum target comprising aluminum in a concentration of about2.0 atomic percent to either about a 50 Å or about a 100 Å thicknessover an ALD TaN layer. The resulting substrates were annealed at atemperature of about 450° C. for a time period of about 30 minutes in anambient of nitrogen (N₂) and hydrogen (H₂) ambient. Scanning electronmicroscope photographs showed that there was no significantagglomeration of the copper-aluminum alloy for substrates annealed at atemperature of about 450° C. for a time period of about 30 minutes.

While foregoing is directed to the preferred embodiment of the presentinvention, other and further embodiments of the invention may be devisedwithout departing from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1. A system for processing a substrate, comprising: at least one atomiclayer deposition chamber for depositing a barrier layer comprisingtantalum nitride, wherein the at least one atomic layer depositionchamber comprises a first source providing a tantalum-containingcompound and a second source providing a nitrogen precursor; and atleast one physical vapor deposition metal seed chamber for depositing acopper-containing seed layer on the barrier layer.
 2. The system ofclaim 1, wherein the at least one physical vapor deposition metal seedchamber is a high density plasma physical vapor deposition metal seedchamber.
 3. The system of claim 2, further comprising one or moretransfer chambers for transferring a substrate between the at least oneatomic layer deposition chamber and the at least one physical vapordeposition metal seed chamber.
 4. The system of claim 1, wherein thetantalum-containing compound is an organometallic tantalum precursor. 5.The system of claim 4, wherein the organometallic tantalum precursor isPDMAT.
 6. The system of claim 5, wherein the PDMAT has a chlorineconcentration of about 100 ppm or less.
 7. The system of claim 6,wherein the chlorine concentration is about 30 ppm or less.
 8. Thesystem of claim 7, wherein the chlorine concentration is about 5 ppm orless.
 9. The system of claim 5, wherein the nitrogen precursor isammonia.
 10. The system of claim 1, wherein the tantalum-containingcompound is a tantalum halide precursor.
 11. The system of claim 10,wherein the tantalum halide precursor comprises chlorine.
 12. A systemfor processing a substrate, comprising: at least one atomic layerdeposition chamber for depositing a barrier layer comprising tantalumnitride, wherein the at least one atomic layer deposition chambercomprises a first source providing a tantalum-containing compound and asecond source providing a nitrogen precursor; and at least onedeposition chamber selected from the group consisting of a physicalvapor deposition chamber, an electroless deposition chamber orcombinations thereof for depositing a copper-containing layer on thebarrier layer.
 13. The system of claim 12, wherein the at least onedeposition chamber is a physical vapor deposition chamber.
 14. Thesystem of claim 13, wherein the physical vapor deposition chamber is ahigh density plasma physical vapor deposition metal seed chamber. 15.The system of claim 14, further comprising one or more transfer chambersfor transferring a substrate between the at least one atomic layerdeposition chamber and the physical vapor deposition chamber.
 16. Thesystem of claim 12, wherein the tantalum-containing compound is anorganometallic tantalum precursor.
 17. The system of claim 16, whereinthe organometallic tantalum precursor is PDMAT.
 18. The system of claim17, wherein the PDMAT has a chlorine concentration of about 100 ppm orless.
 19. The system of claim 18, wherein the chlorine concentration isabout 30 ppm or less.
 20. The system of claim 19, wherein the chlorineconcentration is about 5 ppm or less.
 21. The system of claim 17,wherein the nitrogen precursor is ammonia.
 22. The system of claim 12,wherein the tantalum-containing compound is a tantalum halide precursor.23. The system of claim 22, wherein the tantalum halide precursorcomprises chlorine.
 24. A system for processing a substrate, comprising:at least one atomic layer deposition chamber for depositing a barrierlayer comprising tantalum nitride, wherein the at least one atomic layerdeposition chamber comprises a first source providing atantalum-containing compound and a second source providing a nitrogenprecursor; and at least one physical vapor deposition metal seed chamberfor depositing a metal seed layer on the barrier layer, wherein themetal seed layer comprises a metal selected from the group consisting ofcopper, aluminum, magnesium, titanium, zirconium, tin, alloys thereofand combinations thereof.